Formerly maligned and attacked as a parasitic killer of trees, it is now recognized as an ecologically important native plant that has been around for thousands or millions of years. It is, in fact, a keystone player in the oak woodlands — a species that is disproportionately important to other species relative to its abundance. When mistletoe is removed from ecosystems, one-third of the animals, including birds, mammals, and insects, disappear.

As Kate mentioned this, it suddenly clicked together with something I read in Graham Robb’s book, The Discovery of Middle-Earth: Mapping the Lost World of the Celts, regarding a joke the Celts yelled at the Romans during a battle, to the effect that the Romans were so short they had to build ladders to peek over the walls of the cities in Gaul to see what they were doing — and the Romans apparently never got the joke, whether due to poor interpreters in the Roman army, or a kind of humorless literalism on the part of the Romans.

The Romans may have had difficulty with the languages of the Celts, but I suspect that they also suffered from the same kind of humorless narcissism that afflicts most conquerors. Theirs was the clearly superior culture — for the gods’ sake, they had aqueducts! And an Emperor who wore purple. And a war machine second to none. If the barbarians had anything to contribute, they could damn well express themselves in Latin, in ways that sensible, civilized people could understand.

So it occurs to me that when the Roman writers translated the Celtic term for mistletoe as “all-heal,” the odds are pretty good they got it wrong. The Celts might very well have called mistletoe “the healer of the whole,” or what we would call a keystone species: something that, if it goes away, takes with it a third of your ecological biodiversity, thus rendering the forest inhospitable to humans.

Kate goes on in her book to talk about how mistletoe appears to the birds and beasts that live on, around, and even in the mistletoe. Though poisonous to humans, it is safe, delicious, and an important source of calories and protein for birds, squirrels, porcupines, and raccoons, as well as elk and deer who graze under mistletoe-laden oaks hoping for windfalls. Many small mammals shelter or hide inside a ball of mistletoe, while birds nest in them. Some insect species have co-evolved with mistletoe, and depend on it in their breeding cycle.

We don’t really know much about the Druids of the Roman period. It’s possible that they presided over a culture already falling into ignorance and superstition when General Julius Caesar encountered them, and actually thought mistletoe could be made into some kind of healing tonic. Or perhaps, as some have speculated, the Druids were talking about a different plant.

But I find it more natural to believe that something was lost in translation: not a blunder, like pointing to the wrong plant, but a subtlety of language — such as the difference between “all-heal” and “healer-of-the-whole.”